Relevant prior art for laser processing includes the following:
Japanese Patent Publication 2003-195023 discloses a laser machining method of manufacturing micro three-dimensional structures using less than 1 picosecond (10−12) laser. The same reference also discloses the use of more than one laser source to combine the laser beams to form certain structures respectively in a horizontal direction at a predetermined depth.
Japanese Patent Publication 2001-212796 discloses a laser machining method of manufacturing micro three-dimensional structures using less than 1 picosecond (10−12) laser in the Gaussian distribution pattern. A combination of selective colors and materials determines an amount of energy absorption from the laser to form a desired configuration. The specified material layers are stratified to form the three-dimensional structures.
Japanese Patent Publication 2002-311466 discloses a laser machining method of manufacturing optical channels in a core area of a non-linear optical element using femt-second laser having 800 nm wavelength.
Japanese Patent Publication 2002-182546 discloses a method of marking a computer generated hologram inside a glass wall of a container using femt-second (10−15) laser. The same reference also discloses the placement of the marking at different depths by physically moving a lens for focusing the laser along the optical axis.
Japanese Patent Publication 2001-332092 discloses a method of rewriting data bits in a three-dimensional memory medium by using femt-second (10−15) laser by moving the focus point towards the laser source. The rewriting laser has a lower energy level than that of an initial laser writing the original data.
Japanese Patent Publication 5-104276 discloses a method of processing certain materials such as aluminum and copper having a highly reflective surface using a plurality of laser beams including YAG laser. The laser beams are manipulated via a lens, a mirror and a splitter to have a short wavelength (0.53 μm) and a long wavelength (1.06 μm) before combined into a single focused beam. The short-wavelength laser initially processes a surface or shallow portion of the material for a long-wavelength laser process. Subsequently, the long-wavelength laser processes an inner or deep portion of the material below the initially treated surface.
Japanese Patent Publication 5-192779 discloses a method of processing using a plurality of laser beams including YAG laser. A light amount of each of the laser beams having a different wavelength is controlled before reaching a medium having multiple layers of a different material.
Japanese Patent Publication 2002-224873 discloses a method of processing certain materials such as copper having a highly reflective surface using a plurality of laser beams including YAG laser. At least two laser beams including a short wavelength (less than 400 nm) and a long wavelength (400-600 nm) are simultaneously combined into a single focused beam.
Japanese Patent Publication 2000-190088 discloses a method of sequential processing of certain material by a first laser beam and a second laser beam having a third to a fifth of the wavelength of the first laser beam. The second step via the second laser beam performs a cosmetic adjustment.
In the above described laser prior art technologies, laser beams are combined into a single beam to focus upon a common point. In order to form a structure at various depths of the medium, either the laser beam or the medium must be relocated. The laser beam may be refocused at a new depth by adjusting the focus. Alternatively, the medium may be physically moved with respect to the stationary laser beam. Furthermore, since the structure is sequentially formed at a varying depth, the manufacturing process remains to be desired to simultaneously form the multiple structures in order to improve efficiency.